Field of the Invention
Embodiments of the present disclosure relate to a circulating fluidized bed boiler, and more particularly, to a heating surface in a furnace of the circulating fluidized bed boiler.
Description of the Related Art
It is an inexorable trend for a circulating fluidized bed boiler technology to develop in a direction of large-scale equipment and high degree of parameterization. As the boiler capacity increases, the cross section of a furnace is also constantly increasing; as a result, secondary air injected from a wall surface into the furnace is difficult to reach the center of the furnace. At the same time, compared to the area increase of an evaporating heating surface in the furnace, the furnace volume is more significantly increased, which causes exothermic and endothermic imbalance and puts forward a new requirement for heating surface arrangement. In summary, the secondary air penetration and the furnace heating surface arrangement have become a major technology bottleneck, which constraints the circulating fluidized bed boiler from developing in the direction of large-scale equipment and high degree of parameterization.
To solve the above technical problems, a Chinese patent ZL 200710151813.0 discloses a circulating fluidized bed boiler furnace with a water-cooled column, in which a water-cooled column formed by connecting membrane water-cooled walls is provided between an air distribution plate and a ceiling of the furnace to increase the furnace heating surface, and secondary air may be injected into the furnace combustion space through the water-cooled column. Since a secondary air pipe is needed to be placed inside the column, it is necessary to keep a certain amount of pipe arrangement and maintenance space. However, the cross-sections of the water-cooled column at different levels are kept constant, it therefore causes that all the internal space of the water-cooled column at various levels in an up-down direction is relatively larger, it further causes that a distance between the water-cooled column and an outer wall of the furnace is relatively small, especially the upper space of the furnace cannot meet the requirement for arranging a platen heating surface, and it brings about some difficult in distributing gas-solid flow in the furnace.